// ==UserScript==
// @name           Youtube Subtitle Downloader v29
// @include        https://*youtube.com/*
// @author         Cheng Zheng
// @copyright      2009 Tim Smart; 2011 gw111zz; 2014~2021 Cheng Zheng;
// @license        GNU GPL v3.0 or later. http://www.gnu.org/copyleft/gpl.html
// @require        https://code.jquery.com/jquery-1.12.4.min.js
// @version        29
// @grant GM_xmlhttpRequest
// @namespace https://greasyfork.org/users/5711
// @description   Download Subtitles
// ==/UserScript==

/*
  [What is this?]
    This Tampermonkey script allows you to download Youtube "Automatic subtitle" and "closed subtitle".

  [Note]
    If it doesn't work (rarely), try to refresh the page.
    If problem still exists after refreshing, send an email to guokrfans@gmail.com.

  [Who built this?]
    Author :  Cheng Zheng (郑诚)
    Email  :  guokrfans@gmail.com
    Github :  https://github.com/1c7/Youtube-Auto-Subtitle-Download
    If you want to improve the script, Github pull requests are welcome.

  [Note for Developers]
    Few things before you read the code:
    0. Some comments are written in Chinese.
    1. Youtube has 2 interfaces: Material Design and The Old Design.
    2. This code handles both "Auto" and "Closed" subtitles.

  [What is "Tampermonkey"?]
    "Tampermonkey script" means that you needs to install a browser extension called "Tampermonkey" before installing this script.
    Tempermonkey is available for most modern web browsers, such as Chrome, Firefox, Safari, Microsoft Edge, and Opera.

  [Test Video]
    https://www.youtube.com/watch?v=bkVsus8Ehxs
    This videos only has a closed English subtitle, with no auto subtitles.

    https://www.youtube.com/watch?v=-WEqFzyrbbs
    no subtitle at all

    https://www.youtube.com/watch?v=9AzNEG1GB-k
    have a lot of subtitles

    https://www.youtube.com/watch?v=tqGkOvrKGfY
    1:36:33  super long subtitle

  [How does it work?]
    The code can be roughly divided into three parts:
      1. Add a button on the page. (UI)
      2. Detect if subtitle exists.
      3. Convert subtitle format, then download.
  
  [Test Enviroment]
    Works best on Chrome + Tampermonkey. 
    There are plenty Chromium-based Browser, I do not guarantee this work on all of them;
*/

(function () {

  // Config
  var NO_SUBTITLE = 'No Subtitle';
  var HAVE_SUBTITLE = 'Download Subtitles';
  var TEXT_LOADING = 'Loading...';
  const BUTTON_ID = 'youtube-subtitle-downloader-by-1c7-last-update-2021-2-21'
  // Config

  var HASH_BUTTON_ID = `#${BUTTON_ID}`

  // initialize
  var first_load = true; // indicate if first load this webpage or not
  var youtube_playerResponse_1c7 = null; // for auto subtitle
  unsafeWindow.caption_array = []; // store all subtitle

  // trigger when first load
  $(document).ready(function () {
    start();
  });

  // Explain this function: we repeatly try if certain HTML element exist, 
  // if it does, we call init()
  // if it doesn't, stop trying after certain time
  function start() {
    var retry_count = 0;
    var RETRY_LIMIT = 30;
    // use "setInterval" is because "$(document).ready()" still not enough, still too early
    // 330 work for me.
    if (new_material_design_version()) {
      var material_checkExist = setInterval(function () {
        if (document.querySelectorAll('.title.style-scope.ytd-video-primary-info-renderer').length) {
          init();
          clearInterval(material_checkExist);
        }
        retry_count = retry_count + 1;
        if (retry_count > RETRY_LIMIT) {
          clearInterval(material_checkExist);
        }
      }, 330);
    } else {
      var checkExist = setInterval(function () {
        if ($('#watch7-headline').length) {
          init();
          clearInterval(checkExist);
        }
        retry_count = retry_count + 1;
        if (retry_count > RETRY_LIMIT) {
          clearInterval(checkExist);
        }
      }, 330);
    }
  }

  // trigger when loading new page 
  // (actually this would also trigger when first loading, that's not what we want, that's why we need to use firsr_load === false)
  // (new Material design version would trigger this "yt-navigate-finish" event. old version would not.)
  var body = document.getElementsByTagName("body")[0];
  body.addEventListener("yt-navigate-finish", function (event) {
    if (current_page_is_video_page() === false) {
      return;
    }
    youtube_playerResponse_1c7 = event.detail.response.playerResponse; // for auto subtitle
    unsafeWindow.caption_array = []; // clean up (important, otherwise would have more and more item and cause error)

    // if use click to another page, init again to get correct subtitle
    if (first_load === false) {
      remove_subtitle_download_button();
      init();
    }
  });

  // trigger when loading new page
  // (old version would trigger "spfdone" event. new Material design version not sure yet.)
  window.addEventListener("spfdone", function (e) {
    if (current_page_is_video_page()) {
      remove_subtitle_download_button();
      var checkExist = setInterval(function () {
        if ($('#watch7-headline').length) {
          init();
          clearInterval(checkExist);
        }
      }, 330);
    }
  });

  // return true / false
  // Detect [new version UI(material design)] OR [old version UI]
  // I tested this, accurated.
  function new_material_design_version() {
    var old_title_element = document.getElementById('watch7-headline');
    if (old_title_element) {
      return false;
    } else {
      return true;
    }
  }

  // return true / false
  function current_page_is_video_page() {
    return get_url_video_id() !== null;
  }

  // return string like "RW1ChiWyiZQ",  from "https://www.youtube.com/watch?v=RW1ChiWyiZQ"
  // or null
  function get_url_video_id() {
    return getURLParameter('v');
  }

  //https://stackoverflow.com/questions/11582512/how-to-get-url-parameters-with-javascript/11582513#11582513
  function getURLParameter(name) {
    return decodeURIComponent((new RegExp('[?|&]' + name + '=' + '([^&;]+?)(&|#|;|$)').exec(location.search) || [null, ''])[1].replace(/\+/g, '%20')) || null;
  }

  function remove_subtitle_download_button() {
    $(HASH_BUTTON_ID).remove();
  }

  function init() {
    inject_our_script();
    first_load = false;
  }

  function inject_our_script() {
    var div = document.createElement('div'),
      select = document.createElement('select'),
      option = document.createElement('option'),
      controls = document.getElementById('watch7-headline'); // Youtube video title DIV

    var css_div = `display: table; 
    margin-top:4px;
    border: 1px solid rgb(0, 183, 90); 
    cursor: pointer; color: rgb(255, 255, 255); 
    border-top-left-radius: 3px; 
    border-top-right-radius: 3px; 
    border-bottom-right-radius: 3px; 
    border-bottom-left-radius: 3px; 
    background-color: #00B75A;
    `;
    div.setAttribute('style', css_div);

    div.id = BUTTON_ID;

    select.id = 'captions_selector';
    select.disabled = true;
    let css_select = `display:block; 
    border: 1px solid rgb(0, 183, 90); 
    cursor: pointer; 
    color: rgb(255, 255, 255); 
    background-color: #00B75A;
    padding: 4px;
    `;
    select.setAttribute('style', css_select);

    option.textContent = TEXT_LOADING;
    option.selected = true;
    select.appendChild(option);

    // 下拉菜单里，选择一项后触发下载
    select.addEventListener('change', function () {
      download_subtitle(this);
    }, false);

    div.appendChild(select); // put <select> into <div>

    // put the div into page: new material design
    var title_element = document.querySelectorAll('.title.style-scope.ytd-video-primary-info-renderer');
    if (title_element) {
      $(title_element[0]).after(div);
    }
    // put the div into page: old version
    if (controls) {
      controls.appendChild(div);
    }

    load_language_list(select);

    // <a> element is for download
    var a = document.createElement('a');
    a.style.cssText = 'display:none;';
    a.setAttribute("id", "ForSubtitleDownload");
    var body = document.getElementsByTagName('body')[0];
    body.appendChild(a);
  }

  // trigger when user select <option>
  async function download_subtitle(selector) {
    // if user select first <option>, we just return, do nothing.
    if (selector.selectedIndex == 0) {
      return;
    }

    var caption = caption_array[selector.selectedIndex - 1];
    // because first <option> is for display, so index - 1 

    var result = null;
    var filename = null; // 保存文件名

    // if user choose auto subtitle
    if (caption.lang_code == 'AUTO') {
      result = await get_auto_subtitle();
      filename = get_file_name(get_auto_subtitle_name());
    } else {
      // closed subtitle
      let lang_code = caption.lang_code;
      let lang_name = caption.lang_name;
      result = await get_closed_subtitle(lang_code);
      filename = get_file_name(lang_name);
    }

    let srt = parse_youtube_XML_to_SRT(result);
    downloadString(srt, "text/plain", filename);

    // After download, select first <option>
    selector.options[0].selected = true;
  }

  // Return something like: "(English)How Did Python Become A Data Science Powerhouse?.srt"
  function get_file_name(x) {
    // var method_1 = '(' + x + ')' + document.title + '.srt'; // 如果有通知数，文件名也会带上，比较烦，这种方式不好
    // var method_2 = '(' + x + ')' + get_title() + '.srt';
    var method_3 = `(${x})${get_title()}_video_id_${get_video_id()}.srt`;
    return method_3
  }

  // 拿完整字幕的 XML
  async function get_closed_subtitles() {
    var list_url = 'https://video.google.com/timedtext?hl=en&v=' + get_url_video_id() + '&type=list';
    // Example: https://video.google.com/timedtext?hl=en&v=if36bqHypqk&type=list
    return new Promise(function (resolve, reject) {
      GM_xmlhttpRequest({
        method: 'GET',
        url: list_url,
        onload: function (xhr) {
          resolve(xhr.responseText)
        }
      })
    })
  }

  // detect if "auto subtitle" and "closed subtitle" exist
  // and add <option> into <select>
  async function load_language_list(select) {
    // auto
    var auto_subtitle_exist = false;

    // closed
    var closed_subtitle_exist = false;
    var captions = null;

    // get auto subtitle
    var auto_subtitle_url = get_auto_subtitle_xml_url();
    if (auto_subtitle_url != false) {
      auto_subtitle_exist = true;
    }

    // does closed subtitle exists?
    var tracks_xml_string = await get_closed_subtitles();
    captions = new DOMParser().parseFromString(tracks_xml_string, "text/xml").getElementsByTagName('track');
    if (captions.length != 0) {
      closed_subtitle_exist = true;
    }

    // if no subtitle at all, just say no and stop
    if (auto_subtitle_exist == false && closed_subtitle_exist == false) {
      select.options[0].textContent = NO_SUBTITLE;
      disable_download_button();
      return false;
    }

    // if at least one type of subtitle exist
    select.options[0].textContent = HAVE_SUBTITLE;
    select.disabled = false;

    var caption = null; // for inside loop
    var option = null; // for <option>
    var caption_info = null; // for our custom object

    // if auto subtitle exist
    if (auto_subtitle_exist) {
      caption_info = {
        lang_code: 'AUTO', // later we use this to know if it's auto subtitle
        lang_name: get_auto_subtitle_name() // for display only
      };
      caption_array.push(caption_info);

      option = document.createElement('option');
      option.textContent = caption_info.lang_name;
      select.appendChild(option);
    }

    // if closed_subtitle_exist
    if (closed_subtitle_exist) {
      for (var i = 0, il = captions.length; i < il; i++) {
        caption = captions[i];
        let lang_code = caption.getAttribute('lang_code')
        let lang_translated = caption.getAttribute('lang_translated')
        let lang_name = lang_code_to_local_name(lang_code, lang_translated)
        caption_info = {
          lang_code: lang_code,
          lang_name: lang_name,
        };
        caption_array.push(caption_info);
        // 加到 caption_array 里, 一个全局变量, 待会要靠它来下载
        option = document.createElement('option');
        option.textContent = caption_info.lang_name;
        select.appendChild(option);
      }
    }
  }

  function disable_download_button() {
    $(HASH_BUTTON_ID)
      .css('border', '#95a5a6')
      .css('cursor', 'not-allowed')
      .css('background-color', '#95a5a6');
    $('#captions_selector')
      .css('border', '#95a5a6')
      .css('cursor', 'not-allowed')
      .css('background-color', '#95a5a6');

    if (new_material_design_version()) {
      $(HASH_BUTTON_ID).css('padding', '6px');
    } else {
      $(HASH_BUTTON_ID).css('padding', '5px');
    }
  }

  // 处理时间. 比如 start="671.33"  start="37.64"  start="12" start="23.029"
  // 处理成 srt 时间, 比如 00:00:00,090    00:00:08,460    00:10:29,350
  function process_time(s) {
    s = s.toFixed(3);
    // 超棒的函数, 不论是整数还是小数都给弄成3位小数形式
    // 举个柚子:
    // 671.33 -> 671.330
    // 671 -> 671.000
    // 注意函数会四舍五入. 具体读文档

    var array = s.split('.');
    // 把开始时间根据句号分割
    // 671.330 会分割成数组: [671, 330]

    var Hour = 0;
    var Minute = 0;
    var Second = array[0]; // 671
    var MilliSecond = array[1]; // 330
    // 先声明下变量, 待会把这几个拼好就行了

    // 我们来处理秒数.  把"分钟"和"小时"除出来
    if (Second >= 60) {
      Minute = Math.floor(Second / 60);
      Second = Second - Minute * 60;
      // 把 秒 拆成 分钟和秒, 比如121秒, 拆成2分钟1秒

      Hour = Math.floor(Minute / 60);
      Minute = Minute - Hour * 60;
      // 把 分钟 拆成 小时和分钟, 比如700分钟, 拆成11小时40分钟
    }
    // 分钟，如果位数不够两位就变成两位，下面两个if语句的作用也是一样。
    if (Minute < 10) {
      Minute = '0' + Minute;
    }
    // 小时
    if (Hour < 10) {
      Hour = '0' + Hour;
    }
    // 秒
    if (Second < 10) {
      Second = '0' + Second;
    }
    return Hour + ':' + Minute + ':' + Second + ',' + MilliSecond;
  }

  // copy from: https://gist.github.com/danallison/3ec9d5314788b337b682
  // Thanks! https://github.com/danallison
  // work in Chrome 66
  // test passed: 2018-5-19
  function downloadString(text, fileType, fileName) {
    var blob = new Blob([text], {
      type: fileType
    });
    var a = document.createElement('a');
    a.download = fileName;
    a.href = URL.createObjectURL(blob);
    a.dataset.downloadurl = [fileType, a.download, a.href].join(':');
    a.style.display = "none";
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
    setTimeout(function () {
      URL.revokeObjectURL(a.href);
    }, 1500);
  }

  // https://css-tricks.com/snippets/javascript/unescape-html-in-js/
  // turn HTML entity back to text, example: &quot; should be "
  function htmlDecode(input) {
    var e = document.createElement('div');
    e.class = 'dummy-element-for-tampermonkey-Youtube-Subtitle-Downloader-script-to-decode-html-entity';
    e.innerHTML = input;
    return e.childNodes.length === 0 ? "" : e.childNodes[0].nodeValue;
  }

  // return URL or null;
  // later we can send a AJAX and get XML subtitle
  function get_auto_subtitle_xml_url() {
    try {
      var captionTracks = get_captionTracks()
      for (var index in captionTracks) {
        var caption = captionTracks[index];
        if (caption.kind === 'asr') {
          return captionTracks[index].baseUrl;
        }
        // ASR – A caption track generated using automatic speech recognition.
        // https://developers.google.com/youtube/v3/docs/captions
      }
      return false;
    } catch (error) {
      return false;
    }
  }

  async function get_auto_subtitle() {
    var url = get_auto_subtitle_xml_url();
    if (url == false) {
      return false;
    }
    var result = await get(url)
    return result
  }

  async function get_closed_subtitle(lang_code) {
    try {
      var captionTracks = get_captionTracks()
      for (var index in captionTracks) {
        var caption = captionTracks[index];
        if (caption.languageCode === lang_code && caption.kind != 'asr') {
          // 必须写 caption.kind != 'asr'
          // 否则会下载2个字幕文件（也就是这个分支会进来2次）
          // 因为 lang_code 是 "en" 会 match 2条纪录，一条是自动字幕，一条是完整字幕
          // "自动字幕"那条是 kind=asr
          // "完整字幕"那条没有 kind 属性
          let url = captionTracks[index].baseUrl;
          let result = await get(url)
          return result
        }
      }
      return false;
    } catch (error) {
      return false;
    }

  }

  // Youtube return XML. we want SRT  
  // input: Youtube XML format
  // output: SRT format
  function parse_youtube_XML_to_SRT(youtube_xml_string) {
    if (youtube_xml_string === '') {
      return false;
    }
    var text = youtube_xml_string.getElementsByTagName('text');
    var result = '';
    var BOM = '\uFEFF';
    result = BOM + result; // store final SRT result
    var len = text.length;
    for (var i = 0; i < len; i++) {
      var index = i + 1;
      var content = text[i].textContent.toString();
      content = content.replace(/(<([^>]+)>)/ig, ""); // remove all html tag.
      var start = text[i].getAttribute('start');
      var end = parseFloat(text[i].getAttribute('start')) + parseFloat(text[i].getAttribute('dur'));

      // 保留这段代码
      // 如果希望字幕的结束时间和下一行的开始时间相同（连在一起）
      // 可以取消下面的注释
      // if (i + 1 >= len) {
      //   end = parseFloat(text[i].getAttribute('start')) + parseFloat(text[i].getAttribute('dur'));
      // } else {
      //   end = text[i + 1].getAttribute('start');
      // }

      // we want SRT format:
      /*
          1
          00:00:01,939 --> 00:00:04,350
          everybody Craig Adams here I'm a

          2
          00:00:04,350 --> 00:00:06,720
          filmmaker on YouTube who's digging
      */
      var new_line = "\n";
      result = result + index + new_line;
      // 1

      var start_time = process_time(parseFloat(start));
      var end_time = process_time(parseFloat(end));
      result = result + start_time;
      result = result + ' --> ';
      result = result + end_time + new_line;
      // 00:00:01,939 --> 00:00:04,350

      content = htmlDecode(content);
      // turn HTML entity back to text. example: &#39; back to apostrophe (')

      result = result + content + new_line + new_line;
      // everybody Craig Adams here I'm a
    }
    return result;
  }

  // return "English (auto-generated)" or a default name;
  function get_auto_subtitle_name() {
    try {
      var captionTracks = get_captionTracks();
      for (var index in captionTracks) {
        var caption = captionTracks[index];
        if (typeof caption.kind === 'string' && caption.kind == 'asr') {
          return captionTracks[index].name.simpleText;
        }
      }
      return 'Auto Subtitle';
    } catch (error) {
      return 'Auto Subtitle';
    }
  }

  // return player_response
  // or return null
  function get_json() {
    try {
      var json = null
      if (typeof youtube_playerResponse_1c7 !== "undefined" && youtube_playerResponse_1c7 !== null && youtube_playerResponse_1c7 !== '') {
        json = youtube_playerResponse_1c7;
      }
      if (ytplayer.config.args.player_response) {
        let raw_string = ytplayer.config.args.player_response;
        json = JSON.parse(raw_string);
      }
      if (ytplayer.config.args.raw_player_response) {
        json = ytplayer.config.args.raw_player_response;
      }
      return json
    } catch (error) {
      return null
    }
  }

  function get_captionTracks() {
    let json = get_json();
    let captionTracks = json.captions.playerCaptionsTracklistRenderer.captionTracks;
    return captionTracks
  }

  // Input a language code, output that language name in current locale
  // 如果当前语言是中文简体, Input: "de" Output: 德语
  // if current locale is English(US), Input: "de" Output: "Germany"
  function lang_code_to_local_name(languageCode, fallback_name) {
    try {
      var captionTracks = get_captionTracks()
      for (var i in captionTracks) {
        var caption = captionTracks[i];
        if (caption.languageCode === languageCode) {
          let simpleText = captionTracks[i].name.simpleText;
          if (simpleText) {
            return simpleText
          } else {
            return fallback_name
          }
        }
      }
    } catch (error) {
      return fallback_name
    }
  }

  function get_title() {
    return ytplayer.config.args.title;
  }

  function get_video_id() {
    return ytplayer.config.args.video_id;
  }

  // Usage: var result = await get(url)
  function get(url) {
    return $.ajax({
      url: url,
      type: 'get',
      success: function (r) {
        return r
      },
      fail: function (error) {
        return error
      }
    });
  }

})();